| Object Our purpose is to explore the characteristics of NK cells’ immune reconstitution after umbilical cord blood stem cell transplantation(UCBT), then further identification the character and function of CD3-CD16+CD56-NK subset.Methods In this study, we selected 60 cases patients who were treated by UCBT with myeloablative conditioning regimen as the experimental group, 30 cases of bone marrow transplantation / peripheral blood stem cell transplant patients(BMT / PBSCT) as the case-control group, 21 cases of healthy persons as the normal control group. We detected and their subsets by multicolor flow cytometry at the different time after transplantation and the expression of CD11 b, CD27 and CD57 on CD3-CD16+CD56-NK subset. Then we selected 14 UCBT patients randomly, detected the expression level of their surface activation and inhibitory receptors and the secretion level of TNF、IFN-γ、granzyme and perforin. Finally, we also detected CXCR4 molecule expressed at NK cell surface in the 14 UCBT patients’ peripheral blood and bone marrow, analyzing its chemotactic function.Results 1. In general, the frequency of NK cell in lymphocytes was below in UCBT receptors compared with PBSCT/BMT group within two years, but the absolute number was below only in implanted and 1 month after transplantation. 2. Compared with PBSCT / BMT group and normal control group, the percentage and absolute number of CD3-CD16+CD56-NK subset in UCBT receptors who transplanting time is greater than 4 months were abnormally higher(p<0.05).3. According to the expression of CD11 b and CD27 molecules in NK cell surface, the CD11b+CD27- subset was the main component of CD3-CD16+CD56-NK cells(> 80%), which was consisted with the CD3-CD16+CD56dimNK cells, it proved that the CD3-CD16+CD56-NK cells growth phase is relatively mature, and they own strong killer function. The expression of CD57 molecule on the surface of CD3-CD16+CD56-NK subset was significantly lower than CD3-CD16+CD56dimNK subset in the early 3 months(p <0.0001),while it has no significant difference at 4 month to 2 years between the two subsets.4. Compared to CD3-CD16+CD56dimNK subset, activation receptor NKG2 D, NKp46 and NKp30 expression had a significant reduction in CD3-CD16+CD56-NK subset(p <0.01),but NKP44 expression had no significant difference(p>0.05). Inhibitory receptor NKG2A/CD94 and CD158 a expression were also significantly reduced(p<0.05), but CD158 b expression had no significant difference(p>0.05); Granzyme B and the intracellular TNF expression by CD3-CD16+CD56- NK cells were significant lower than CD3-CD16+CD56dimNK cells(p<0.05). While the expression of granzyme A 、perforin 、IFN-γ and CD107 a had no significant difference between the two subsets.5. The expression of CXCR4 on CD3-CD16+CD56-NK subset and CD3-CD16+CD56dimNK subset cell in UCBT patients’ peripheral and bone marrow had no significant difference. But compared with normal control group, the expression level of CXCR4 in UCBT group was increased significantly(p<0.05).Conclusions 1. NK cells were reconstituted early after UCBT, and the percentage and absolute number of CD3-CD16+CD56-NK subsets were increased significantly. Compared with the cytotoxicity CD3-CD16+CD56dimNK cells, the differentiate stage and function-related phenotypes of CD3-CD16+CD56-NK cells subset are in mature state.2. CD3-CD16+CD56-NK cells are high expressioned of CXCR4 molecule in UCBT patients,and this is the foundation of NK cells chemotaxis to bone marrow to occur GVL effect.3. CD3-CD16+CD56-NK cells subset may have a certain correlation with GVL effect after transplantation. But it is through the direct reaction or after further differentiation and proliferation to magnify the GVL effect is still unclear, sorting the corresponding NK cells to confirm the results are needed. |
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